Study and Application of Electron Probe Micro-analysis Dating for Uraninite

Based on the theory of radioactive decay and the hypothesis that the initial lead is little enough to be neglected in the measured mineral and the system of U, Th and Pb is closed, electron probe micro-analysis (EPMA for short) dating method is applied to calculate the age of uranium minerals or U-bearing minerals with the contents of U, Th and total Pb measured by EPMA，and with formulae (1). This method was first proposed by Professor Suzuki K. (Suzuki, K. and Adachi, M., 1991) who works in Nagoya University, Japan, and is mainly used in the micro in-situ dating of monazite and zircon, and rarely in that of uranium minerals and other U-bearing minerals. At present, isotope dilution method is the main technique for the dating of uranium minerals. However, this method is useless for the uranium minerals which are very tiny in size (usually several micrometers) and can not be purified. If these kinds of uranium minerals meet the hypothesis as mentioned earlier, they can be dated by EPMA dating method which is advanced in micro and insitu analysis and to fill up the deficiencies of traditional dating methods. The research results and application examples of EPMA dating for uraninites are illustrated in this paper.